Magnetron with valence electrode



Jan. 26, 1954 c v L|TTON 2,667,580

MAGNETRON WITH VALENCE ELECTRODE I Filed Oct. 20, 1949 2 Sheets-Sheet' lTo ANTENNA INVE NTOR CHARL E5 M L/7'7'0N ATTORNEY Jamzfi, 1954 c. v.LITTON MAGNETRON WITH VALENCE ELECTRODE 2 Sheets-Sheet 2 Filed Oct. 20,1949 w mft wzwti INVENTOR CHARLES V. L/TTON ATTORNEY Patented Jan. 26,1954 UNITED STATES PATENT OFFICE MAGNETRON WITH VALENCE ELECTRODECharles V. Litton, Redwood City, Calif. Application October 20, 1949,Serial No. 122,391 8 Claims. (01. 250-36) The present invention relatesto a generator of ultra high frequency waves of high power andparticularly to a generator of the magnetron type.

To obtain a larger amount of power at high frequencies the magnetrongenerator has been most useful. The magnetron is made large to increasethe power output. It is sometimes difficult to design magnetrons withthe desired power handling capacity for operation at high frequenciesbecause the higher the frequency the smaller the magnetron must be.Therefore it has been proposed to connect a plurality of magnetrons inparallel. In such an arrangement there are many modes of operationobtainable and therefore the device is unstable.

If one considers a magnetron with twelve vanes defining the resonantcavities, there are at least five simple modes of operation in whichundesired oscillations tend to build up an infinite number of modesbeing possible since the resonators have distributed constants. Ifseveral such magnetrons are coupled to a common output, there would notonly be the modes of the individual tubes but also the modes availableby combination of one tube with the others. In the case where ten tubeswith twelve vanes are stacked, there would be at least 50 possible modeswhich would strongly disturb oscillation in the desired mode at thedesired frequency.

It is therefore the object of this invention to provide an arrangementof oscillators preferably magnetrons intercoupled in such a way that thenumber of possible modes at which the scillators will operate issubstantially decreased.

More specifically it is an object of this invention to provide anarrangement of magnetrons which will oscillate at only a single mode.

These objects are obtained by interconnecting said oscillators ormagnetrons by coupling units which have a length a multiple of a halfwave length such that no energy is exchanged between the oscillatorcircuits or resonators of the magnetrons when they are oscillating atthe same frequency. Then if one drifts from the desired frequency,energy will be exchanged and the result will be that the severalinterconnected oscillators or magnetrons will tend to pull each otherinto oscillation at the same frequency.

The above mentioned objects and features of this invention will bebetter understood by reference to the following detailed description ofa preferred embodiment given in connection with the accompanyingdrawings of which Figures 1, 2 and 3 show diagrammatic sketches ofcoupling arrangement used in explaining my invention;

Figure 4 shows a diagrammatic sketch of six magnetrons coupled togetheraccording to my invention; Figure 5 shows in cross-section twomagnetrons coupled together and with output coupling means in accordancewith an embodiment of my invention; Figure 6 shows a diagrammatic sketchof three magnetrons stabilized according to my invention; and Figure '7shows a diagrammatic sketch of two magnetrons stabilized by doublebonding therebetween in accordance with my invention.

In Figure 1 there is shown two cavity resonators I and 2 of two separatebut similar magnetrons. These resonators are connected together by atransmission line which is a wave length or an integral multiple of awave-length long at the frequency in. If these magnetrons are operatingin the same mode and at the same frequency and if there is no phaseinversion in the coupling, there will be no net exchange of energybetween the two resonators when they are exactly in phase.

The figure shows arrows representing current flow at an instant of timeto. There will actually be no current flow through the coupling wavepath since the cavity resonators are oscillating in phase and are ineifect coupled in parallel. The high frequency voltages across both endsof the wave path are of the same magnitude and. phase. Any current whichthe energy from the resonator I would tend to transmit to resonator 2will be balanced by the current which the energy from resonator 2 wouldotherwise transmit through the coupling wave path.

In Figure 2 the two resonators I and 2 of the two separate but similarmagnetrons are shown directly connected together. The transmission linea wave length long as shown in Figure 1 acts just as the closely coupledarrangement shown in Figure 2. When the two resonators I and 2 in eitherof these figures are oscillating at the same frequency and in phase andin the same mode no net exchange of energy will occur between them.

In Figure 3 the two resonators I and 2 of the two separate but similarmagnetrons are shown coupled by a transmission line a half wave lengthlong with no phase inversion in the coupling. In such a case there is nonet exchange of energy when the currents in the two resonators of thetwo separate magnetrons are out of ]phase. As is obvious, thetransmission line must 3 long where 7\ is the operating wave length andn is an integer. This is also true of the case where the coupledresonators are oscillating in phase and there is phase inversion in thecoupling.

If for any reason one of the magnetrons drifts or otherwise changes infrequency, the interconnected system of any of Figures 1, 2 or 3 will nolonger be balanced. The equilibrium thereof will be disturbed and anenergy exchange will occur which will exert a stabilizing force on oneor the other or both of the cavity resonators until equilibrium isrestored. The action is quite like that occurring amongst the se arateresonators of the multi-cavity magnetron itself. The latter is a closelycoupled system of parallel res= onant elements which lock; intosynchronisrn at a single frequency. Similarly the closely coupledinterconnected system of magnetrons, two of which are shown in Figures1, 2 or 3, is synchronizedto'gether and may hunt but does so systemwiseas a whole. Such hunting would normally. evidence itself as a suddenchange from one operating frequency to another.

In Figure 4 there is shown diagrammatically an arrangement of six'rnagnetrons interconnected in accordance with my invention. Each of the'magnetrons g'through 8 is provided with a'cathode 9 and six vanes In.These vanes define six cavity resonators. A corresponding cavityresonator in each magnetron is coupled together by a transmission pathll to a similar cavity resonator of an adjacent magnetron. Thusmagnetron 3 is coupled to magnetron 4 and magnetron 4 is coupled tomagnetron 5 and so forth; magnetron 8 being coupled between magnetrons iand 3, thus forming a closed loop. The coupling between magnetrons 8 and3 is not necessary. Each of the interconnecting trans mission paths H isshown adjustable in length. As'pointed out in connection with theFigures 1, 2 and 3 the length of the interconnecting lines order thatthe magnetrons may be in synohronism or equilibrium at the operatingfrequency is either an odd or an even multiple of a half wave lengthlong at this frequency depending upon the relative phasingof the oscillations inv the coupled cavity resonators and the sense of the coupling.When the coupling line H; betweenmagnetron's 3 and 4 is of the properlength so; that there will be no not exchange of energy at the desiredfrequency it, these two resonators will oscillate at the frequency f andif the magnetrons tend to drift or otherwise change in frequency thecoupling line II will function to pull them back intoequilibrium. Thiswill be true of all of the magnetrons 3 through 8 In addition magnetrons3 and 8 are connected together by a transmission path H. Thus if anymagnetron in the loop tends to drift or change in frequency all of theothers will function to pull it back to the operating fred ejr' cy, 7 VK Separate output connections i2 are shown from each magnetron.Obviously these may be coupled to separate loads, such as to separate ae nasg i ana ienna ar a or h y may be all'coupled in parallel to asingle load, thus pro-- viding a large amount of power at the ultrahighfrequency at which the magnetrons are oscillating.

It will be apparent thatan arrangement of magnetrons as shown in Figure4 will tend to oscillate at those frequencies for which theintercomiecting transmission paths are an odd or even multiple of a half-wave length long depending upon the phasing of the interconnectedcavity resonators. Thus a harmonic series of frequencies may beobtained. To eliminate these harmonically related frequencies, thelengths of the interconnecting wave paths may be made different integralmultiples of a half wave length of the desired frequency so as toprovide additional asymmetry to undesired modes. In the schematicillustration in Figure 4 interconnecting path ll between magntrons 3 and4 may be made m. long with no phase inversion in the coupling and thepath ll between resonators 4 and 5 may be made long with phase reversalin the coupling to resonat'or 5. Then the even harmonics will beeliminated as the path which is necessarily a half wave length long atthe operating frequency will not permit them.

A wave transmission path H" is also shown coupled between two of thepaths H which form the ring of interconnected magnetrons This path isalso adjusted so that there'will be no net exchange of energy betweenthe magnetrons when they are all oscillating in the desired mode. Itprovides improveaperrormanee of the maj netron and reduces the h'untingas does the path between the resonators 8 and 3 as pointed out above.

Wave guides may be usedto interconnect the magnetrons but it has beenfound that transmission lines are better since they may be tuned withgreater stability than wave guides. Guide wave length changes relativelyrapidly with frequency and wave guides are therefore relatively moreunstable. On the other hand, wave guides are more efficient means forcoupling to a had than transmission lines. The preferred arrangeinent isshown in Figure 5.

In Figure 5-, two magnetrons i3 and 25 are shown in cross section. Thesemagnet-fans rep resent any two of the magnetrons 3-, E, 5; 1-, and 8shown in Figure 4. Each of these "magnetrons is provided with six vanesFrom one cavity resonator i6 ofni'a'gnet'ron l3 there is provided anoutput coupling arrangement I! which matches the impedance ofthe'cavity' re'sonator'as seen at gap I 8 to the impedance *ofa coaxiaIline I9; The-coaxial 1-1116 I83 202s coupled by a similar matchingsection M to a cavity resonater 22 of the magnetron M and the line I9,20 together with the matching sections l1 and 21 is adjusted'to be aneven or odd multiple of a half wave length long depending on whether ornot the interconnected resonators are oscillating in phase or out ofphase and depending on the sense of the coupling. intermediate the endsof the transmission line I9 213 "isp-rovide'dapair of telescoping lines23, 24 closely fitting over the conductors "of, the transmission linei9; 28!. The transmission line is formed. from two separate parts whichmay be separatedand thus the telefscoping sections 23 and fit-serve toadjust'the length of the. coupling; transmissionline. From?anothercavity resonator *of magnetron 1'8:

there is provided amatching section zesimuar tomatching sections H and-2in This is shown separated by one, resonator from resonator l6 and asalternate resonatorsof a magnetron 'os'c'ila late in phase, resonator 25will oscillate in phase; with resonator i6. A similar output matchingsection 21* ifs-provided; from a resonator 2'8f'in ma netronlx4sgwhichfresonator will also oscillate:

in phase with oscillations in resonator 22. In such an arrangement thecoaxial line I9, together with the matching sections I1 and 2| areadjusted to be a multiple of a wave length long at the desired operatingfrequency. From a cavity resonator 29 which is chosen so that it willalso oscillate in phase with cavity resonators 6 and there is providedan output impedance matching section which matches the impedance of thecavity resonator as seen at gap 3| to the impedance of a wave guide 32which is shown coupled to matching section 30. A similar arrangement 33,34 is shown for the magnetron It is apparent that each interconnectingline need not be limited to the coupling and stabilizing of only twomagnetrons. For example three magnetrons may be stabilized by anarrangement as shown in Figure 6.

Resonators 35 and 36 of magnetrons 31 and 38 are connected together by awave transmission path 39. The resonators are presumed to be oscillatingin phase. The connection of path 39 to resonator 35 is reversed withrespect to the connection to resonator 36 and so the length of the path39 is an odd multiple of a half wave length of the operating frequency.Thus magnetrons 31 and 33 are stabilized.

Magnetron 40 is also stabilized by means of a. transmission path 4|connected from one of its resonators 42 to transmission path 39.Resonator 42 is taken to be a'resonator of magnetron 40 that isoscillating in phase with resonators 35 and 36. The connection of path4| to resonator 42 is in the same sense as the connection of path 39 toresonator 35. Therefore the total path between these two resonatorsshould be an even multiple of a half wave length. If the connection ofpath 4| to path 39 is made at a point an odd multiple of a half wavelength from resonator 35, then the length of path 4| should also be anodd multiple of a half wave length. Then the total length of wavetransmission path from resonator 42 to resonator 36 is an odd number ofhalf wave lengths and since these resonators are oscillating in phaseand since the connection to one resonator is reversed in sense withrespect to the connection to the other, this is the correct length forstabilization.

It is also evident that more than one path may be connected between anypair of magnetrons in order to couple them closely and insurestabilization.

In Figure 7 there is shown two wave transmission paths 43 and 44 each ofwhich couples together a pair of cavity resonators of each magnetron 45and 46. These paths are shown coupled between resonators of eachmagnetron which are oscillating in phase and they are shown with 180phase inversion in the coupling. Therefore they are made an odd multipleof a half wave length long at the desired frequency. In particular path43 is shown long and path 44 is long. This double bonding may be appliedto any number and arrangement of interconnected magnetrons.

While I have described my invention in connection with a magnetronoscillator it will be apparent that the invention is not limitedor-restricted to this type of oscillator. Furthermore while I have showncoaxial lines interconnecting the cavity resonators of the magnetronsand while I have shown a wave guide formed by a metal wall, it will beapparent that the interconnections used might also be two wiretransmission lines or dielectric wave guides.

It will be understood therefore that the embodiments shown and describedherein, are to be regarded as illustrative of the invention only and notas restricting the appended claims.

I claim:

1. An arrangement for the production of ultra high frequency energy ofhigh power with means for stabilizing the frequency of oscillationscomprising a plurality of oscillators each having a plurality ofresonators and output coupling-units from more than two of saidresonators, one of said coupling units of each of said oscillators beingan output load coupling unit, an ultra high frequency transmission pathconnecting each of the remaining coupling units of each of saidoscillators to a remaining coupling unit of another oscillator, saidtransmission paths and said coupling units being matched to saidresonators and having a length a multiple of a half wave length suchthat no energy is exchanged between the resonators when they areoscillating at the same frequency.

2. An arrangement according to claim 1 in which said transmission pathsconnecting said oscillators comprise paths a multiple of a wave lengthlong connecting resonators of said oscillators which are to oscillate inphase and paths an odd multiple of a half wave length long connectingresonators that are to oscillate out of phase.

3. An arrangement according to claim 1 in which said transmission pathscomprise coaxial lines and said output load coupling units comprise waveguides.

4. In an arrangement for the production of ultra high frequency energyof high power comprising a plurality of magnetrons each having aplurality of cavity resonators, a means for stabilizing the frequency ofsaid magnetrons comprising at least two output coupling units from tworesonators of each magnetron, and two transmission paths each anintegral multiple of a half wave length long and interconnecting tworesonators of one magnetron with two resonators of another magnetron.

5. An arrangement for the production of ultra high frequency energy ofhigh power with means for stabilizing the frequency of oscillationcomprising a plurality of magnetrons each having a plurality ofresonators, an output coupling unit including a resonator-towave-guidematching section coupled to one resonator of each said magnetron, a waveguide connected to each of said above-mentioned coupling units, a pairof output coupling units including a resonator-to-coaxial-line matchingsection coupled to two additional cavity resonators of each of saidmagnetrons, a transmission path connecting each of saidresonator-to-coaxial-line matching sections of one of said magnetrons toone of said sections of another of said magnetrons, said transmissionpaths including coaxial lines matched to said matching sections andhaving a length a multiple of a half wave length such that no energy iexchanged between said resonators when they are oscillating at the samefrequency. 1

, e351; arrangement for the; production of ultra high frequency energyof high power witn means for stabilizing the ir queney 0f oscillationcomprising a plurality of oscillators eaen havinga plurality of tunedcircuits and qouplingruints from more than two of said tuned circuits;one of said'cou'plmg un'itsof each of said oscillators being an outputcoupling unit, an ultra high fre quency transmigsion path conneetin eachof the remainin coupling units of each of said pscma tors to a remainingcoupling unit Of another 6S= cillator, said transmission paths and saidcoupling units being matched. to said tuned circuits and having a lengtha m'uitiple of a half wave length such that no energy is exchangedbetween said tuned circuits when they are osciliating at the samefrequency.

'7. An arrangement according to claim 5 in which said transmissionline's connect said mag= netrons in a closed system.

a. An arrangement eeeeramg to claim 5 in which saidtransmi'ssion lin'eare connected eaen between one of said resofiator-to-coexm-nnematchir'ig sections and 'a common junction point of all or saidtransmission paths. v

CHARLES v. LIT'ION.

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